Method of cooling molds

ABSTRACT

A method of water-cooling molds for casting steel ingots in which the molds are air-cooled in a cooling pit until their surface temperature is between about 500* C. and about 300* C., and then water-cooled by jetting cooling water onto the molds.

United States Patent Ogi et al.

[ 51 Mar. 7, 1972 [54] METHOD OF COOLING MOLDS [72] Inventors: l-lideoOgi; Haruo Ozaki; Masai-u Mishiro; Yoshikazu Horikawa; Shunii Mori, allof Kitakyushi Japan Sept. 22, 1967 Japan ..42/60482 Nov. 2, 1967Japan..... ..42/70266 [52] US. Cl ..62/62, 164/121, 164/126,

164/128 [5 1] Int. Cl ..F25d 31/00 [58] Field of Search ..l34/l7, 94, 22R, 99, 30, 102,

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ulbunch $8 COOLING TEMPERATURE IN "C [56] References Cited UNITED STATESPATENTS 3,204,301 9/1965 Flemings, Jr. et al. I 64/1 26 X 3,321,0075/1967 Cofer et al. 1,336,459 4/ 1920 Woodward 164/128 PrimaryExaminer-Meyer Perlin Assistant Examiner-Ronald C. CaposselaAttorneywenderoth, Lind & Ponack [57] ABSTRACT A method of water-coolingmolds for casting steel ingots in which the molds are air-cooled in acooling pit until their surface temperature is between about 500 C. andabout 300 C., and then water-cooled by jetting cooling water onto themolds.

1 Claims, 4 Drawing Figures COOLING TIME IN HOURS PMENTED R 7 I972COOLING TEMPERATURE IN "C SHEET 1 OF 2 FiG. 2

M H. w ,11

OGI HIDEO OZAKI HARUO MISHIRO MASARU YOSHIKAZU HORIKAWA MORI SHUNJI I NVEN T'Olk {Punk PATENTEDHAR 71912 3, 646,772

sum 2 or 2 061 HIDEO OZAKI HAR INVENTORs MISHIRO MASARU YOSHIKAZUHORIKAWA MORI SHUNJI y wmm M METHOD OF COOLING MOLDS This application isa division of application Ser. No. 762,230, filed Sept. 16, I968 now USPat. No. 3,548,845.

BACKGROUND OF THE INVENTION 1. Field of the The Invention This inventionrelates generally to a method of cooling molds and the like and moreparticularly to a method of watercooling molds for casting steel ingots.

2. Description of the Prior Art I In steel making plants,conventionally, in order to increase the frequency of the use of moldsfor casting ingots, just after the ingots are extracted, the molds arequickly cooled by aircooling or water-cooling so they can be used again.

However, when such molds are cooled by air-cooling, there aredisadvantages that it takes a long time to cool them down to about 100C. at which they can be used and that a large mold cooling area isrequired.

On the other hand, when the molds are to be cooled by water-cooling,they are dipped into a water tank or water is jetted on them andtherefore there are the disadvantages that a large volume ofnontransparent white smoke or white smoky stream is generated whichcauses difficulty in the operation of an ingot crane installed indoors,and, due to the thermal stress and the nonuniformity of cooling of theinner surface of the thus quickly cooled mold, the inner surface will becaused to crack and the life of the mold will be shortened and thesurface condition of the steel ingot cast in such mold will not be good.Further, there has been suggested a method wherein, in order to preventthe generation of a large volume of white smoke or steam, for example,molds are mounted on a moving carriage and are water-cooled while theyare passed through a special mold cooling chamber. However, in saidmethod, there is the disadvantage that an additional crane operation andcorresponding equipment are required to load and unload the movingcarriage with molds as well as the above-mentioned disadvantages due tothe quick cooling of molds.

SUMMARY OF THE INVENTION An object of the present invention is to solvesuch problems as are mentioned above by using both air-cooling andwatercooling and to provide a method for cooling molds wherein molds canbe reasonably cooled within a comparatively short time.

Another object of the present invention is to provide a method forcooling molds and the like by which it is easy to control the moldtemperature, thereby stabilizing the quality of steel ingots.

In order to attain the above-mentioned objects, many molds at a hightemperature just after steel ingots are extracted from them are placedin a cooling pit in which the molds are air cooled until their surfacetemperature is between about 500 C. and about 300 C. Thereafter they arewater cooled to less than 100 C. by a water-cooling apparatus which ispositioned above the above-mentioned cooling pit, and which carries outwater-cooling by spraying cooling water onto the molds and adjusting thequantity of water so that the maximum cooling velocity at the time ofthe above-mentioned air-cooling of the mold will not be exceeded. Thewater-cooling apparatus comprises a gate-shaped moving deck providedwith means for jetting cooling water onto the molds and mounted so as torun above the said mold cooling pit, a cooling water channel extendingalong rails on which said moving deck runs, a cooling water suction pipeextending into said water channel and communicating with theabove-mentioned cooling water jetting means, a water-sealed exhaustconduit formed by partitioning off a part of the above-mentioned coolingwater channel, and an exhaust hood provided on the above-mentionedmoving deck with an exhaust conduit pipe extending therefrom into saidwater sealed exhaust conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a curve showing the relationbetween the mold temperature after the ingot is extracted and thecooling time and showing a comparison of the air-cooling method and themethod according to the present invention;

FIG. 2 is an elevation view, partly in section, of an example of thewater-cooling apparatus used in carrying out the method according to thepresent invention;

HO. 3 is a plan view of the apparatus of FIG. 2; and

FIG. 4 is a general plan view of a mold treating area equipped with thewater-cooling apparatus as shown in FIGS.

2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of thepresent invention will be described in the following with reference tothe drawings.

From FIG. 1 showing an example of an air-cooling curve of a mold whenusing a conventional air-cooling system, it is seen that, in order tocool a mold from its temperature just after an ingot is extracted fromit to a suitable temperature for the next use, which is below about C.and at which the inner surface of the mold can be given proper care,about 13 hours are required as shown by the curves A and B.

On the other hand, in the present invention, the cooling process isdivided into two stages and, in the first cooling stage, though therewill be variations depending on the size of the mold, the mold is cooledby air-cooling for about 4 to 5 hours to a temperature between about 500C. and about 300 C. along the curve A, because, as understood from thecooling curve, even if the mold is left to cool in a position in whichthe mold temperature is high, the cooling velocity will be high and,even if the mold is water-cooled thereafter, no defect such as thecracking of the mold will be caused below such temperature. Then, in thesecond cooling stage shown by D after the first cooling stage, the moldis uniformly watercooled for about 0.2 to 1.5 hours so that it is below100 C. with showers of water from above the mold by a water-coolingapparatus to be used in the present method. In such case, the relationbetween the mold temperature and the cooling time is as in the curve E.Further, the quantity of the cooling water is adjusted so that thecooling velocity in the second cooling stage does not exceed but issubstantially equal to the maximum cooling velocity in the abovementioned first cooling stage. Generally, as understood from the coolingcurve, in a situation in which the mold temperature is high to beginwith, if air-cooling is carried out, needless to say, a very long timewill be required to cool the mold down to the required temperature but,in two stage cooling wherein the mold is initially cooled from the hightemperature by air-cooling and is watercooled to the final lowtemperature, as described above, the mold can be cooled at a velocitysubstantially equal to the maximum cooling velocity during air-coolingall through and the defects due to the quick water-cooling of the moldcan be prevented. In addition, if the mold is water-cooled at a velocitywhich exceeds the maximum cooling velocity of aircooling, needless tosay, the mold will be caused to crack. Further, because the moldtemperature in the second cooling stage is less than about 500 C., thevolume of the nontransparent white smoky steam will be much smaller thanif watercooling is carried out throughout the entire cooling operation.In this method, by using the water-cooling apparatus, all of the steamis caught and is discharged out of doors as described later.

A preferred embodiment of the mold water-cooling apparatus for use inthe method of the present invention will be explained in the followingwith reference to the drawings.

In FIGS. 2 and 3 casting molds l are conveyed into a cooling pit I8after a steel ingot is extracted from them and a gateshaped moving deck2 is mounted on rails 3 provided on both sides of the cooling pit l8.Said moving deck 2 has a plurality of running wheels 4 which run to andfro on the above-mentioned rails 3. A cooling water channel is providedon one side of the cooling pit 18 and below the bottom of the pit 18,and has a water-sealed exhaust conduit 14 defined by a dependingshielding plate 13 having the upper edge fixed in airtight fashion to abeam 16 extending along the upper part of one side of said water channel5. The lower edge of said shielding plate 13 is spaced from the bottomwall of the channel 5. In the water channel 5 below the plate 13 ispositioned the lower U-shaped part 12 of an exhaust conduit 11, theupper end of which is connected with an exhaust hood provided on theupper part of the above mentioned moving deck 2. The U- shaped part 12extends under the lower edge of shielding plate 13 and opens into theabove mentioned exhaust conduit 14 formed by the shielding plate 13 andrunning parallel with the water channel 5. A suction pipe 6 providedwith a strainer has its lower end in the water channel 5. A pump 7 isfixed to the upper end of said suction pipe 6. A cooling water pipesystem 8 arranged in the form of a lattice is mounted on the lower partof the girder of the moving deck 2. Water jetting nozzles 9 are fixed tosaid piping. An exhaust port extends from the above-mentioned exhaustconduit 14 out of the area so that steam generated by cooling the moldsand caught by the above-mentioned exhaust hood 10 will be led into theexhaust tunnel 14 and then discharged from the exhaust tunnel 14 throughthe exhaust port 15.

The mold cooling area provided with the cooling apparatus shown in FIG.2 is shown in FIG. 4. An exhaust fan 19 is connected with theabove-mentioned exhaust port 15 and provided between the pillars 24 ofthe building. An exhaust chimney is connected to said exhaust fan 19outside the building. Rails 21 and 22 form a track for pulling in awater pouring carriage and for cars for receiving cooled molds.

The operation of the cooling apparatus to carry out the method accordingto the present invention will now be further explained.

Many molds 1 having had ingots extracted by a mold crane are immediatelyconveyed by the same crane to the mold cooling area, are placed in thecooling pit 18 and are naturally aircooled. By said natural air-cooling,the first cooling stage is finished and the molds are between about 500C. and about 300 C. The second water cooling stage is carried out byrunning the gate-shaped moving deck above the molds 1. In said secondcooling stage, the cooling water in the water channel S is first suckedup through the suction pipe by the pump 7, is then pressurized and isjetted toward the molds 1 in the pit from the water jetting nozzles 9through the piping 8. A large volume of white smoky steam generated atthe time of jetting the cooling water is sucked into the exhaust hood 10above the water jetting nozzles 9 by the suction from the exhaust fan19, is drawn through the exhaust conduit pipe 11 and is then dischargedinto the exhaust conduit 14 through the U-shaped exhaust pipe part 12positioned in the water channel 5. The white smoke in said exhaustconduit 14 is further sucked by the exhaust fan 19 through the exhaustport 15 and is forcibly exhausted out doors. Further, as the shieldingplate 13 is air tightly fixed to the beam 16 as mentioned above,atmospheric air is completely prevented from coming in and, as theshielding plate 13 is spaced from the bottom of channel 5, the movement(in the direction indicated by the arrow in FIG. 4) of the U-shapedexhaust pipe part 12 during the running of the deck is not obstructed.At any position along the cooling pit 18, the cooling water can becontinuously sucked up and the generated steam can be continuouslyexhausted.

The water level 17 in the water channel 5 is kept always at a constantvalue by a level gauge and the quantity corresponding to the quantity ofwater used for cooling is automatically supplied.

The molds l cooled to below C. in the second cooling stage as mentionedabove may be moved to any other place and may be treated there so as tobe used again. Or else, for example, the inner surfaces of the molds maybe swept and inspected from the gate-shaped moving deck and may bepainted with oil with a laterally traveling carriage 25 attached to themoving deck 2 as shown in FIG. 3. Further, once the relation between thetemperature of the mold to be cooled in the second cooling stage and thetime is established. even if the temperature is not measured each timethereafter. the cooling can be adjusted and therefore the operation isvery easy.

As described above, according to the mold cooling method of the presentinvention, the long time of about l3 hours required for the conventionalair-cooling can be shortened to about 5.5 hours without impairing thedurability of the mold. That is to say, according to the presentinvention, not only can the time required for cooling be shortened, butalso the frequency of use of the mold can be increased and the spacerequired for the mold cooling place can be kept small and the number ofmolds needed can be greatly reduced.

An advantage of the present invention is that it makes it easy tocontrol the temperature of the molds, thereby stabilizing the quality ofsteel ingots poured and solidified in the molds. 1n the case of rimmedsteel ingot, for example, whether its quality is good or not, dependsalso on the degree to which blow holes are present near the surface ofthe ingot. The part of the ingot where no blow holes or very few, ifany, exist, is called solid skin, the thickness of which is related tothe temperature of molten steel in the ladle on one hand, and is greatlyinfluenced by the temperature of the mold on the other hand. It has beenascertained that the thickness of said skin is reduced unless thetemperature of the mold is below a certain point, say, C.

in this case, it is easily understood that cooling according to themethod of the present invention to achieve rapid cooling of the usedmold is preparation for next use in as short a time as possible, is veryuseful for stabilizing the quality of steel ingots.

In addition to the above advantages, cooling water used in the coolingaccording to the present invention rinses the dust out of the inside ofthe mold, resulting in a smooth,'beautiful surface of the steel ingots.

The method according to the present invention has been described asbeing for the cooling of molds for steel ingots. However, the presentinvention is not limited to this use, but is also applicable to thecooling of cast products in general and all other things to be cooled.

What is claimed is:

1. A mold cooling method comprising placing in a cooling pit a pluralityof molds from which ingots have been extracted after being cast,air-cooling said molds until their surface temperature becomes betweenabout 500 C. and about 300 C., and then after terminating air cooling,jetting cooling water on said molds to cool them down to a temperaturebelow about 100 C., and adjusting the quantity of cooling water so thatthe water cooling rate does not exceed the maximum air cooling rate.

